Don't you get Outlook security warning when you try to send email from your program?

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>I need to send "automatically" e-mails and I added sample BUTTONS.VCX class library to my project.
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>I've read a few articles about this question and I'm not doint anything different from the examples I saw.
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>But...
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>If I try to send to "someone" an "unespecified error ocurrs" If I don't indicate a recipient Ms Outlook is displayed and everything seems to be fine.
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>I though; What about setting Outlook Express as default mail client?
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>Wonderfull!!! No errors.
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>Any of you knows the secret cause MS OFFICE OUTLOOK 2007 returns an error if I set "recipientaddress" property?
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>I must say I use MS Outlook as my main mail program and also use Outlook Express. Both work very well.
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>Thank you very much.
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> Héctor